Process controllers don't do windows

Embedded operating systems dominate the process control market, but this soon could change according to Senior Technical Editor Dan Hebert in his monthly Technically Speaking column for CONTROL.

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By Dan Hebert, Senior Technical Editor

What is the most widely used operating system in your process plant? Hint: It is not Windows. It is non-Windows embedded operating systems that reside in controllers, field devices, drives, and just about any other microprocessor-based control system component. Why should you care? Because these off-the-shelf embedded operating systems are reducing the cost and increasing the performance of all microprocessor-based control system components. In the future, desktop computers may use an embedded operating system running between Windows and the computer hardware to create a secure computing environment.

Commercial off-the-shelf (COTS) hardware and software have become ubiquitous in process plant control systems over the past few years. This trend was first visible with the Wintel standard for HMIs. The trend intensified with the widespread adoption of Ethernet as the standard for higher-level process plant communications.

The final frontier for the COTS trend is real-time process control and monitoring. The list of vendors that now use COTS embedded operating systems reads like a who’s who of the process control marketplace. Emerson, Invensys, Honeywell, Yokogawa and many others employ COTS operating systems because these systems deliver better performance at a lower cost than internally developed operating systems.

Foxboro uses COTS embedded operating systems in their I/A Series controllers and in their new interface modules. “Given the speed of development required to produce new products, and the fact that there is already a large and vibrant field of third-party suppliers, process control vendors are not likely to devote their own resources to developing operating systems,” says Alex Johnson, the Foxboro system architect at Invensys Process Systems.

The only exception to the COTS embedded operating system trend seems to be specialized control components like handheld devices that absolutely need to wring every last ounce of performance from hardware. These components often employ custom proprietary operating systems.

Although there are a multitude of players, the leaders in the COTS embedded operating system market are Linux and embedded non-Windows versions of Microsoft software. It is no surprise to see Microsoft in a position of leadership, but Linux is usually not considered a major player by process control end users. This is not the case for process control vendors, many of whom have embraced the open-source software.

SoftPLC uses embedded Linux operating systems in their real-time process control systems. They chose Linux because it is royalty-free and because they wanted access to the source code to fix problems andadd specialty enhancements. “We created our own Linux operating system based on our specific requirements, and we also included some patches that we have submitted and had accepted to the overall development effort,” reports Cindy Hollenbeck, the executive vice-president of SoftPLC.


According to Bob Karschnia, the director of technology at Emerson Process, his company also uses Linux for their “high-end systems.” Sixnet uses Linux in their DCS controllers, remote terminal units, and their industrial Ethernet managed switches. “We believe there is definitely a trend towards off-the-shelf operating systems such as Linux,” says Mike O'Connor, the product marketing manager at Sixnet. “We are a prime example of that trend.”

“For many years we created and maintained a proprietary OS, but it became harder to provide advanced features. We loved having full control over the source code but didn’t like having to write everything from scratch. Linux is a perfect solution. It’s open, flexible, and widely supported. It allows us to offer just about any modern software capability that users could ask for,” concludes O’Conner.

COTS embedded operating systems are mostly transparent to the end user, but this could change due to demands for increased security, better performance, and increased uptime.
New generations of microprocessors can easily accommodate simultaneous operation of two operating systems.Embedded operating system vendors say that an ideal solution to computer crashes, worms, and viruses is to put a secure operating system between the computer hardware and Windows.

VxWin from Wind River runs between Windows XP embedded and the computer hardware. System reliability is enhanced because VxWin continues to operate if a faulty driver causes a Windows XP Embedded system exception to occur.

Green Hills Software calls this dual operating system approach a virtual machine. According to Green Hills, the use of their embedded operated system between Windows and the system hardware guarantees that their will be no software-related systems failures and no susceptibility to viruses and worms. Green Hills Software is used in a wide variety of mission critical applications including “fly-by-wire” systems in commercial aircraft.
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